When a new Deploy Action is added to an Automation Campaign, a copy of the List Definition is created as a child of the List Definition selected in the Deploy Action. If the original List Definition had no From Address defined at the time the copy was created, then the copy will also have no From Address. To verify the child List Definition has a From Address defined:

Go to LISTS > LIST DEFINITIONS.

Next to the List Definition associated with the Automation Campaign, click VIEW LISTS.